This invention relates to a reproduction machine capable of making duplex copies from a set of original documents. More particularly, it involves a control system for automatically adjusting the reproduction process of such a machine in the event of a fault condition so that the selected number of copies are ultimately produced even though some copies may have been lost due to the fault occurring during the middle of a copy run.
As processing speeds of modern day reproduction machines become increasingly faster, and machine accessories such as sorters, collators, binders, document handlers, etc. become more prevalent, the problem of recouping or saving a specific job in the event of a machine malfunction or fault condition, such as, for example, a paper jam, becomes almost impossible. It will be understood that protection against fault conditions like paper jams is provided through safety controls designed to stop the machine, as well as any accessories used therewith. The jammed papers, which are usually damaged or mutilated, are then removed and the machine restarted. However, loss of these partially processed copies upsets the copy run, since, if the system is merely restarted, the number of copies made will not equal the number of copies selected. This, of course, is due to the loss of some copies in clearing the machine.
Thus, to ultimately produce the number of copies selected, some provision for making up the copies lost as a result of clearing the jam must be made. Unfortunately, this is an extremely task in modern high speed reproduction machines, particularly those employing accessories such as a document handler, since it is difficult to determine exactly how many copies are actually lost and to identify those copies lost with the correct original. Rather than go through a complicated evaluation, many users may tend to simply start the entire copy run anew, discarding even those copies which have been successfully completed. This, of course, can be quite wasteful and expensive, particularly where the job is large and almost completed at the time of the jam.
As described in U.S. Pat. No. 3,944,794 to Reehil et al, the Xerox 9200 copier/duplicator system incorporates a jam recovery technique that has proven to be extremely satisfactory. However, this machine does not include provision for automatically making two sided or duplexed copies. Instead, it merely provides the capability of producing one sided or simplex copies automatically. It is realized that some of the more recent commercially available machines provide the capability of automatically producing duplex copies. However, due to the extreme complexity of such machines, they have not included provision for automatically remaking lost copies in the event of fault conditions.